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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
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<body>
  <script>
    // 打印100以内所有偶数的和
    var sum = 0
    for (var i = 1; i < 100; i++) {
      // 判断i是否是偶数
      if (i % 2 === 0) {
        sum += i
      }
    }
    console.log(sum)
  </script>
</body>
</html>